The "front" door of the super mutant infested building will spontaneously open when you approach up the ramp with the door closed. This will also happen even if there are no living non-player characters around.
The super mutants outside of the Outcast outpost, in the infested building, spawn quicker than most super mutants, which can be a problem for higher-level characters.
Bailey's Crossroads, VA is an actual suburb of Washington, D.C., located not far from its in-game location. It is known for large groups of apartment buildings, which may be the basis of the Outcast Outpost and its surrounding areas. The suburb is named after Hachaliah Bailey, ancestor of James Anthony Bailey, of Barnum & Bailey's Circus. There is in fact not a Metro stop at Bailey's Crossroads.